Constructor

Motivation

• Manually setting attributes (as in Classes And Dictionaries) is clumsy

• Typos/bugs ahead

• ⟶ want a well-defined object initialization

• ⟶ want to require user to pass firstname and lastname

class Person:
    def __init__(self, firstname, lastname):
        self.firstname = firstname
        self.lastname = lastname

• Calling the type ⟶ __init__()

person = Person('Joerg', 'Faschingbauer')
f'firstname: {person.firstname}, {person.lastname}'

'firstname: Joerg, Faschingbauer'

And self?

• class Person ⟶ object of type type

• Types are callable ⟶ creates instance

• If class has __init__ method defined, then that is called to initialize the object

• Invoked with two parameters

  person = Person('Joerg', 'Faschingbauer')
  

• Called with three parameters

  class Person:
      def __init__(self, firstname, lastname):
          ...
  

  • The object being constructed

  • The instance under construction

• Object being initialized: self (name self is only convention)